In 1978, he traveled to San Salvador, along with his wife Doris, to serve at the Iglesia Nazaret as senior pastor.
Bush led the movement of missions called COMIBAM from Latin America during its initial phase and later served as CEO of Partners International from 1986 to 1992, an organization that seeks to grow communities of Christian witnesses in largely non-Christian areas by partnering with indigenous Christian ministries.
[1] He and his wife Doris coined the term 10/40 Window, which focused on the region of the world with least exposure to Christianity.
The 4/14 Window is a global Christian mission movement focused on delivering children between the ages of 4 and 14 years old from oppression, deception, depression and destruction.
The study of catalytic antecedents of today’s mission led to a World Inquiry conducted from 2002 to 2004 involving participants from more than 700 cities.